Group B streptococci (GBS) are the leading cause of human neonatal pneumonia, sepsis and meningitis in the United States. The high incidence of infant mortality associated with GBS infection has led to a significant research effort focused on GS pathogenesis and the identification of virulence-related factors. However, the characteristics of GBS that are critical to the virulence of this pathogen and disease progression largely remain unknown. The long-term goals of this proposal are to gain a better understanding of the molecular basis for BS virulence in the human host and to identify important protein targets for the development of preventative and therapeutic measures such as vaccines and novel antimicrobials. Specifically, the aims of this proposal are to isolate putative virulence proteins from GBS and investigate the role of these proteins in the disease process. Gene fusion technology using alkaline phosphatase as a reporter enzyme will be employed to isolate secreted proteins from GBS, which are thought to be enriched for factors that participate in bacterial-host cell interactions, and have been shown to contribute to bacterial virulence in other microbial systems. Bacterial strains deficient for the putative protein effectors will be constructed and examined in vivo animal sepsis and infection models, which, in concert with in vitro cell-culture adherence and invasion assays, will help to characterize the function of the identified proteins and their importance in disease. The isolation of putative protein effectors from GBS is hoped to help identify future targets for therapeutic studies and development to provide treatment and protection against GBS infection.